This invention relates to a composite, drum type container for storing and dispensing easily vaporizable fluids, and more particularly to a composite, drum type container comprising an inner corrosion-resistant liner and an outer shell designed to resist high internal pressure caused by vaporization of the fluid.
Containers, particularly large constructions useful for containing liquids and gases under high pressure, are at present usually built of metal and/or laminated composite materials because of the high resistance required in order to withstand high axial and radial pressures. Containers made of metal are very time-consuming and costly to build because of the need first to produce the various components of the container and then to assemble them together, e.g. by welding. Moreover, a high degree of expertise is required because if the welding (or other bonding technique) used for assembling the components together is not perfectly executed, leaks may develop during the use of the container. Further, metal containers tend to corrode, oxidize, pit or develop unpleasant odors or tastes, unless non-corrosive metals are used, such as stainless steel, or protective layers or coatings are applied, both of which substantially increase the expense and/or time in producing the containers. Corrosion or oxidation of metal containers can result in contamination of the liquid contents with metallic ions. Building containers made from laminated composite materials is also time-consuming, expensive and expertise-dependent because of the need to manufacture the components and then assemble them together.
Containers made of plastics such as polyethylene are known in the art, and such containers may be manufactured by rotational molding, which is a relatively low cost molding process. Such containers typically are composite in that they comprise an inner plastic liner and an outer, rigid plastic shell. The outer shell of the composite structure typically serves as protection of the inner liner as well as providing a means by which the container can be handled via drum handling equipment. While such plastic containers overcome many of the disadvantages of metal containers, it is difficult to construct a plastic container that will withstand high pressure, i.e., on the order of 43 p.s.i. The ability to withstand high pressure is important in containing chemical compounds, such as hydrochloric acid and ammonium hydroxide, which have high vapor pressures. If the container is not sufficiently rigid, the ends of the container may deform under high pressure, causing leakage and swelling, and preventing the container from fitting into existing, standard size bulk chemical delivery system cabinets. Further, such containers are often manufactured in non-standard shapes because of the requirements for both axial and radial rigidity, again preventing them from being fitted into standard delivery systems.
Another problem with existing chemical containers is that they typically have flat tops and bottoms. Not only are flat tops and bottoms subject to deformation under pressure, but they also prevent complete, i.e., 100% dispensing of the contained liquids and thorough rinsing of the container after dispensing the contained liquid.
There is a need for a composite, drum type plastic container of standard dimensions, i.e., no larger than a standard 55 gal. drum, with an improved ability to resist deformation caused by internal pressure. The container should be relatively inexpensive to manufacture, and should be capable of dispensing 100% of its contents and easy rinsing and cleaning. The container should also be pallet stackable with other containers of similar dimensions.